Control means for transmitting systems



Aug. 9, 1932. R. 1 DAVIS CONTROL MEANS FOR TRANSMITTING SYSTEMS Filed Feb. 1. 1927 WTNESSES'I Fatentecl Aug. 9, 1932 Urrea raras isi-,95

ROBERT L. DAVIS, OF PITTSB''BJGH, PENNSYLVANIA, ASSIGNOR TO VJESTINGHOUSE ELECTRIC @t llA'rl'TlAC-TURING- COMPANY, A CORPORATION OF PENNSYLVANIA CONTROL MEANS FOR TRANSMITTING SYSTEMS Application filed February 1, 1927. Serial' No.

My invention relates to radio transmitting systems, and it has particular relation to s ystems designed for the optional transmitting of telegraphic or telephonie signals.

One object of my invention is to provide 'a transmitting system that will consume m1111- mum power when in operation.

Another object of my invention is to provide a transmitting system wherein no power will be radiated during the intervals between keying, or when modulation current is absent.

Another object ot my invention is to provide duplex transmitting system, in which a receiving instrument is automatically disconnected from the antenna during keying intervals, and connected thereto during spacing intervals.

Another object of my invention is to provide in a transmitting system of the type described, a dual system of control, permittingl the output of the system to be modulated from a plurality of separate points.

Another object ot my invention is to provide a duplex radio transmitting system particularly adapted for use on shipboard, in which the circuit network utilized for the radio output control may also be utilized for communication between separated points.

In the operation of transmitting systems which radiate a considerable amount of power, it is highly desirable that every precaution be taken to minimize power waste, and to reduce the wear and tear on the expensive thermionic devices involved. To this end,

certain carrier wave suppression systems have been designed, in which the unmodulated carrier wave is never radiated, radian tion taking place only upon modulation besupplied. ilth ougl carrier-wave suppressing systems are an improvement over systems which permit the radiation of the carrier at all "L times, yet they do not, in general, provide for the suppression of the direct current component in the plate circuits of the various tubes during non-signalling intervals. In large installations, even though carrier wave supil' pression is practised, the tubes are subjected to constant wear, and terioration is rapid. l

One phase of the present invention, therefore, is concerned in providing means 'for stopping the plate current in all tubes of a transmitting system during non-signalling periods. This result I accomplish by normally applying to the grids of all the tubes a negative potential suiciently high to stop all plate current, changing this negative potential to the proper operating potential vby means of a manually controllable relay. The relay may be either under the control of a telegraph key, or may be actuated by a pushconsequently their debutton located contiguous to the microphone used for voice modulation, suitable additional switching arrangements beingY also provided whereby the system may beadapted to telegraphy or telephony at the option of the operator.

Inasmuch as duplex, or break-in operation is highly desirable in'point-to-point communication, I have also provided a system of relays whereby a radio receiver is placed in circuit with the transmitting antenna during non-keying, or non-signalling intervals. The relay system is arranged to be controlled by the telegraph key, or the push-button aboverefered to, depending on whether signalling is being carried on by telegraph or telephone. i

I have, inv addition, provided a systeml of circuit connections whereby the radio transmitter and receiver may be distantly controlled from a plurality of points. rllhis feature is of distinct value on ship board, enabling either the radio operator, or a distantly situated ships oilicer, to operate the transmitter.

The novel features which are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, bothas to its organization and method of operation,`tol

getherpwith further objects and advantage thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing.

The single figure of the drawing is a diagrammatic view of a transmitting system incorporating a preferred form of my invention.

Referring to the drawing, I have illustrated my invention as applied to a telephone transmitter constructed according to the present trend ofthe art. Such a transmitter usually comprises a speech amplifier, a modulater, a master oscillator, and a power amplifier, each stage including a plurality of -power tubes connected in parallel. In order to avoid a multiplicity of detail, each group of parallel-connected tubes has been represented in the drawing as a single tube, and each group will be referred to as though it comprises but a single tube as shown.

A speech amplifier tube 1, having a lilament 2, a grid 3 and a plate 4, is provided `withan input circuit comprising the second- .of an laudio frequency transformer 6, :and an output, or plate circuit, comprising the primary 7 of an audio frequency transformer 8. y

AAc'modulator tube 11, lhavinga filament 12, `a grid l3vand a plate 14, has an input cir- .cuit,comprisingthesecondary of the audio frequency transformer 8, and an output cir;

-cuit including ;a modulation choke-coil 16.

rOne end of the modulationcholre-coil is con- .nectedto the I,output circuit of the Yspeech amplifie-r and to a contact element 17, while the -end of the choke nearest the modulator plate is connected Lto a contact element 18.

The grid circuits of the speech amplifier :and modulator :tubes-are connected in parallel through a biasing battery 19 to a contact ele- .ment 21. Y l

O nefilament terminal of the speech ampliv"lier Ytube and one filament terminal of the modulator tube areconnected to a conductor .22 which is connected to the'secondary winding 23 of a lament heating transformer 24, 'the primary winding 25-of which is supplied with alternatingcurrent from a source 26. .The-other filament terminals of the speech amplifier tube Vand 'the modulator tube are connected to a conductor 27 which-leads to a `Contact element 28, with which element cooperates a switch member 29 connected to the .other terminal of the secondary winding 23 .through va conductor 31. Y

A master oscillator tube comprising a yfilament 36, a grid 37 and a plate 39, has a frequency determining circuit comprising an inductor 41 shunted by a tuning condenser :'42, this -circuit being' Yconnected to the grid 37 through aconductor 43 and to the plate 39 through a condenser 44. A resistor 40 `is connected across the filament power sup- .ply leads 22 and 31, and a connection 38 is A' ,made between a mid-point thereof and 'a mid-point on the inductor 41. Filament power for the oscillator -tube is supplied from the filament transformer 24, while -plate -potential is supplied through a conductor 45 terminating in a movable switch member 46 and a fixed contact member 47. rlhe grid 37 is Connected through a resistor 50 to a conductor 52, one end of which terminates in a movable switch member 51, and the other end of which is connected to the armature 53 of a relay 54 and to the negative end 55 of a resistor 56 connected across a generator 57 arranged to supply high potential for the plates of the various tubes.

The positive pole of the generator 57, and the shunting resistor 56 are connectedto a movable switch member 58 by means of a conductor 59. A condenser 61 is connected across the terminals of the generator 57, this condenser being of relatively large size, pref erably about five microfarads.

A power amplifier tube 70, having Aa filament 71, a grid 72 and a plate 73 has 4its grid coupled to the output circuit of the master oscillator through a coupling 'con-4 denser 74. rlhe grid circuit of the power amplifier tube includes a resistor which is connected to the relay armature 53. The purpose of the connections Vbetween the grids of the various tubes and the relay armature 1" will be later explained in detail.

The filament of the power amplifier ris Aconnected across the secondary winding 23 of the filament transformer 24, while the plate is connected through a coupling in ductcr 76 to the `conductor45. It will .be noted thatthe power amplifier and master oscillator tubes are connected in parallel, insofaras the plate potential is concerned, and that ythe output of both `will therefore be modulated when the system is used for telephony. This rather unusual ymethod of connect-i on seems to permit of more complete modulation than is possible with the sys- Atems of the customary type.

l' The coupling inductor 76 is placed in inductive relationship with an inductor-77 in- -cluded in an antenna system .7 8. The larmature 79 of a relay 81 is included inthe antenna system 78, rand associated therewith is a lower contact element 82 connected'to .ground through a conductor 83, andan up- Iper contact element 84 connected to ground by way of a radio receiving device 85.

rlhere'lays 54 and 81 are connected in series with a telegraph keying device 90, which maybe of any desired type, automatic, or manual, and operating current for these relays is provided from a battery 91.

The contact element 92 associated with the armature 53 of the relay 54 is connected to a point 93 near the negative end of the resistor, and is also connected to the mid-point of the resistor 40 by a conductor 94. In order that the potential of the mid-point of ythe resistor 40 may be fixed, it is provided with a ground connection :95. A large condenser 100, preferably of about one microfarad capacity, is connected across "the armature 53 and the Contact element 92. This I 3 condenser prevents sparking at the opening and closing of the contacts.

The keying device90 is shunted by a circuit comprising a conductor 96 terminating in a movable switch arm 97, and a second conductor 98 terminating in two contact meinbers 99 and 101 associated with the movable members 102 and 103 of an interphone switching device y104. f

'Ihe movable switch arm 97 is'asso'ciated with a contact elem-ent 105 which is connected through a conductor 106 to the contact element `107 of a relay 108, the movable armature 109 of which is connected by a concluetor 111to the movable members 102 and 103 of the interphone switching device 104. This switching device also comprises two addi'- tional movable members, 112 and 113, these members being connected by a conductor 114 to an audio-frequency choke-coil 120 in the output circuit of the radio receiving device 85, and by a conductor 116 to one terminal of the primary winding 1,15 of the speech amplifier input transformer 6. rlfhe other terminal of the Winding 115 is connected by a conductor 118 through the actuating winding of the relay 108 and a source of potential 119, to a conduct-or 121 connected between telephone substations 122 and 123. rl`he actuating winding of relay 108 is also connected by a conductor 125 to Va conductor 126 ei;- tending between the stations 122 and 123. At station 122 the conductor 126 terminates in a. contact element 127 associated with a circuit closing device 128 and a'se'cond contact element 129. The contact element 129 is connected through a telephone head-'set 131 and a conductor 132 to a Contact! element 133 associated with the movable member 112 of the switching device 104.

At station 123 the conductor 126 terminates in a contact lelement 134 associated with a circuit closing device 135 which cooperates with a contact element 136, from whichelement a circuit may be traced through a telephone head-set 137, and a conductor 138, to a contact element `139 associated' with the movable member 113 of the switching device 104. f

An actuating device 141 is arranged to permit simultaneous control of the movable members 102, 103, 112 and 113, Vof the interphone switch 104.

ln addition to the telephone-head set, telephone station 122 comprises a microphone 142, a calling buzzer or bell 143, and a circuit closing device comprising a movable element 144 having cbntact elements 1,45 and i 146 associated therewith. A hook-switch 147 is also provided, with which cooperates a contact element ,148 connected to the buzzer 143.

The telephone station 12,3 comprises in addition to the telephone headset 137, a microphone 152, a calling buzzer or bell 153, and

also at station 123 a hoolr-switch157 cooperating with a contact element 158 connected to the buzzer 153. Y l The hook-switch 147 at station 122 is connected to one terminal of the head-set131, Y .to the contact element 129, and toa conductor 159 which yextends to the hook-switch`157 located at station 123. At station 123 the hook-switch 157 is connected to one terminal of the'telephone head set 137 and to the contact element 136.

r`A. condenser 161, preferably of approximately five microfarads capacity, is connected between conductors 126 and 159, while a similar condenser 162 is shunted around the relay 108 and the battery 119.

The output circuit of the radio receiving device 85 is connected through a stopping condenser 163 anda conductor 164 to the contact element 136, which element is in turn connected to the headset 137 and, through the conductor 159, to the headset 131.

In order that the operation of invention may be made clear, it is first assumed that unmodulated telegraphic signals are to be transmitted. In such event, there is no necessity for energizing the speech amplifier and the modulator, and the switch-arms 29, 51, 46, 58 and 97 are removed from the contact elements 28, 21, 18, 17 and 105, thus opening thev circuits through which the speech amplifier and modulator are supplied with .lament power, plate potential and grid bias.

A further movementfof the switch arm 58 causes it to make contact with the contact-element 47, thusconnecting the positive pole of the generator 57 to the bus 45, supplying plate potential to the master oscillator and power amplifier. rllhe five switch arms referred to may obviously be interconnected for simultaneous actuation, and this manner of connection lis vpreferably employed in an actual embodiment of my invention. y l

The filaments of the master oscillator and of the power amplifier tubes may now be energized from the source 26 and, by reason of Y the connections from the frequency determining circuit 41, 42 to the plate and grid of the oscillator tube, oscillations will be generated provided the grid bias potential of the oscillator tube is of the proper value. The generated oscillations will be amplifiedI in the power amplifier, and may be radiated as a radio-frequency wave from the antenna.

Itis believed obvious that signalling may be accomplished by interposing a telegraph key in the plate circuit of either the master oscilA` lato-r tube or the power amplifier tube, or in the antenna-ground system.` In these positions, however, the key would necessarily be forcedto handle a large amount of power,

and would be subjected tol destructive sparlring. I prefer, therefore, to interrupt the Agenerated train of oscillations by periodically making the grid potential of the master'oscil- -lator so negativethat oscillations cannot be generated, and-by also simultaneously making the grid of the power amplifier so negative that oscillations, eventhough generated, cannot be amplified therein.v The manner in which I accomplish the alteration of the `grid potentials at signal frequency will;now;be.,.explained. v v.

Assume that the interphone switching device 104 is in theposition shown in the drawing, in which position the contact elements 99 and 101 are disassociated from the cooperating movable members 102 and 103, andthe circuit shunting the telegraph keyi90isy open. As lono as the key 90 is open, the grids 37 and 72 are n-egatively biased by the drop- .in potential from the point 93 on :the resistor 56 to the negative terminal of the source 57, the point 93 being grounded'and being connected tothe resistor shunting the filament leads 22 and 31. The total value of the resistor 56, in an actual installation, is 40,000l

ohms, the valuebetween the point-s 93 and 55 is 110,000 ohms, and the applied potential approximately 1,200 volts, which places the point approximately 300 volts Vnegative with respect to the filaments. Such bias is amply suliicient to block both the oscillator and power amplier tubes. Y

Upon closing the key 90, relays 54 and 81 are energized, armature 53 and contact 92 cooperating to'short circuitzthat portion of the resistor 56 which lies between theV points 93 and 55. The negative bias is consequently removed from thegrids 37 and 72, thus permitting the generation and radiation of oscillations whenever the key is depressed.

Upon energizing the relay 81, armature 79 makes Contact with element 82, thus completing the circuit to ground for the vradiating structure. In its up, or normal, position, armature 79 makes contact with element 84, completing rthe antenna circuit to ground through the radio receiver 85.v

VIt is thus apparent that 4the system does not generate or radiate oscillations during spacing intervals and, that valso during such spacing intervals the radio receiving set is in operative condition. ,s

The circuit .for thereceived signals may be traced through condenser 16,3 over conductor 164 vthrough the head set 137,.con ductor 138, contact 139, movable `member 113 and conductor 114. lAnother receiving circuit may beftraced through condenser 163,

Jconductor 164, conductor 159,'headset 131,

conductor'132, contact 133, movable lelement 112 and conductor 114 back to the receiving set output choke. The head set 137 is assumed to be that used by the radio operator while the other lhead set 131maybe located at :any convenient situation lsuch as the chart-room or the bridge.

:The-operation of nay-system, whenusing 'voice modulation will ,now be explained.

The switch arm 29, 51, 46, 58 and 97 are SOV-moved as toz'make-contact with elements 28, 21, 18, 17 kand 105. Filament potential for the speech amplier .and modulator tubes is accordingly applied thereto through conductors 22'and127. lAt the same time, by reason of the contact of arm v58 with clement 17, positivey potential is .applied 4to plates 4 and -14 from the ygenerator V57. The plate 14 is connectedthrough `contact 18, switch arm 46 and'conduetor 45 to the plates of the master oscillator and the power amplifier, the modulation .choke coil 16 being interposed in its usual and well-known position.

The grids 3 and 13 of the speech amplifier and modulator respectively are connected through a biasing battery 19contact 21,

and switch arm51 to the gridbiasbus 52, the further connections of which have been previously explained.

AssumingA that the radio operator desires to control the modulation ofthe transmitted oscillations by means of microphone 152, the arm 141 .of the interphone switch 104 is Vthrown to the right which causes ycontacts Z112 and 133 to open,contacts 99vand 102 to close, while contacts 113 and 139 remain closed. Before Aspeaking into the microphone 152, the button-i154 is pressed, completing the circuit between. contacts 155 and 156. Acircuit may be now traced from the vrpositivepoleof battery 119 through conduc- .tor 120, conductor 121, contacts 155 and 156, microphone 152, contacts 139 and 113, conductor 116, primary windi-ng 115,.relay 108, back to the negative pole of battery 119. The relay 108 thus being energized causes armature 109 to make contact with element 107, placing a shunting-circuit around the telegraph key-90. This circuit'may be traced as follows: 'battery 91, relay 54, switch arm 97, contact 4105, conductor 106,.contact 107 armature 109, conductor 111, contacts 102 and `99, conductor 9 8, .frelay 81I and back to the negative pole of the battery. f

Aspreviously explained, the .energizing of relay y54 removes the blocking bias from the master oscillator and the power amplifier tubes. In view of the fact ythat the grids of `the speech-amplifier'and modulator tubes are also connected to the same conductor 52 .y

completing the circuit across contacts 155 and 156, has supplied the microphone with talking current and has, at the same time, by the action of relay 54, removed the blocking bias from the entire system.

If, therefore, the microphone V152 is energized by speech while the button 154 is depressed, the speech currents will be amplified and the radiated wave will be modulated thereby. Upon pressure being removed from the button 154, blocking bias is again restored to all the tubes by reason of the release of relay 108 andV the consequent deenergization of relay 54. rl`he operator, therefore maintains the button 154 depressed as long as he desires to transmit an upon release of the pressure the oscillations cease and the transmittino' antenna is connected by the action Vof the relay 81 to the receiving set.

lf it is desired that the microphone at station 122 be used for modulating the output of the transmitter, the operating arm 141 of the interphone switching device 104 is thrown to the left, thus opening contacts.v 139 and 113 and closing contacts 103 and 101. By

applying pressure to the button 144 the circuit between contact element 145 and 146 is closed and a circuit may be traced from the positive pole of the battery 119 through l contacts 146, 145, microphone 142, conductor 132, contact elements 112 and 133, conductor 116, primary winding 115, conductor 118, relay 108 and the negative pole ofthe battery 119. rlhe relay 108 is, accordingly, energized and the cycle of operations previously described may be repeated.

If it is desired to communicate between stations 122 and 123 without modulating the transmitting system, the arm 141 of the interphone switch 104 is set in its central posi` tion as shown in the drawing. When the switch is in this position it will be noted tha inasmuch as contacts 99 and 102 and contacts 101 and 103 are disassociated, the shunting circuit comprising armature 109 and contact 107 cannot be completed, with the result that even though relay 108 be energized the blocking potential will not be removed from the tubes. If the radio operator at station 1 .3 desired to communicate with station 122 he removes thehead set 137 from the switch hook 157 and presses the button 135. Binging current is then supplied from the positive pole of battery 119 through conductor 120 to the buzzer 143, through contact 148, switch hook 147, conductor 159, contact 136, contact 134, conductor 126, conductor 125 and back to the negative pole of the battery 119 to energize the buzzer 143. The party at station 122 then removes the head set 131 from the switch hook 147 and presses the talking button 144 in order to energize the microphone 142. The direct current supply for the microphone 142 may be traced over a circuit as follows; from the positive pole of the battery119 through-conductor 120, contacts Y146 and 145, microphone 142, contact element 133, movable arm 112, conductor 116, primary winding 115, relay 108 and back to the negative pole vof battery 119.

In order that the microphone at station 123 may be supplied with direct current it is necessary that the talking button 154 be held depressed, closing the circuit between contact lnsofar as the voice, or alternating, com-y ponent of the microphone current is concerned, the headsets 131 and 137 are effectively in parallel with both microphones. A common terminal of the headset 137 andthe microphone 152 is connected to the corresponding common terminal of the headset 131 and the 4microphone 142 through a circuit whichmaybertraced over conductor 138, contaw elements 139, 113, 112, 133 and conductor 132. The remaining terminals of the head sets are connected directly together by the conductor 159, and an audio frequency path from this 'conductor may be traced to the lower terminal of each microphone through the condenser 161, battery 119, conductor 121 the contacts of either talking button 144 or 154.y

irrespective of which microphoneV is energized by the closing of the circuit through the cor-responding talking button, both headsets will be energized by the alternating component of the voice currents, but this double energization is not disadvantageous.

-itis thus apparent that a transmitting system constructed according to my invention is extremely versatile. It is easily adapted to either speech modulation or to telegraphy, the change from one to thev other being accomplished by merely throwing a single switch. It is also apparent that a transmitting system, according to my invention, is economical in operation, inasmuch as all the thermionic devices involved consume energy only during actual signalling periods and not during spacing periods, or periods when voice modulation is not impressed upon the system. It is also apparent that by reason' of the circuit connections illustrated and described I have provided a system whereby a radio transmitter maybe satisfactorily controlled from' a plurality of distant points.

Y My system has a further advantage in that it permits communication between the separate radio controlling stations over the same conductors that are utilized to control the radio transmitter, while preventing the currents used in such station-to-st-ati on communication from influencing the output .of the radio transmitter, even though-the `transmitter may-be energized. I am aware that break-in systemsanalogous to the system herein describedY have been previously proposed. It is'my belief, however, thatno previous break-in system deenergizes the transmitter completely atsuch times asthe antenna is connected tothe radio receiving device. The combination ofbreak- Vin relays and complete de-energization is one that I believe to be distinctly new Aan-d-original with me. Y

f Although I have illustrated and described a specific embodiment of my invention, many modifications thereof will be suggested to those skilled in the art. My invention is not to be limited, therefore, except insofar as is necessitated by the prior art and bythe spirit ofthe appended claims. e I claim as my invention:

l. In a radio transmitting system,thermi onicmeans for generating radio frequency oscillations, modulating meanstherefor comprising a microphone and a plurality ofthermionic devices, a source of energizing current for said microphone, and means whereby all of said therniionic devices are -placed in an inoperative state upon deenergization of said microphone.

2. In a. radio transmitting system, a plurality of thermionic devices adapted to generate and transmit radio frequency energy, modulating means'therefor comprising a plurality of .tliermionic devices, a radiating structure, a radio receiver, an antenna, a microphone arranged to control said modulating means, a source of energizing current for said microphone and means whereby the energizing of said microphonecontrols instrumentalities for placing all of-saidthermionic de- 7ices in an operative state, for permittingthe energization ofvsaid antenna,and for disconnecting said receiver from said antenna. 3. In a radio transmitting system, a pluralityof thermionic `devices adapted to generate Y and transmit signal-modied radio-frequency energy, means comprising a microphone g anda source of current therefor for modifysaid energy, means yfor normally biasing said thermionic devices to an inoperative state', andmeans whereby the connection of said microphone to said current source causes the removal of said bias. Y

. 4. In combination, a therlmionic device so arranged as to be capable of'generating oscillations, means for normally .biasing said device to the inoperative state, means comprising a microphone for modulating said oscillations, a current source for said microphone, and means whereby the energization of said microphone from said current source causes theremoval of the bias from the ther-` mionic device.

5. In a signalling system, an antenna, a ra'dioreceiving means associatedftherewith, a

plurality of tliermioiiic devices for. generat- ROBERT L. DAVIS. 

